Dealing with GParamSpec is tedious and less efficient than necessary.
GParamSpec is a data type meant to be used to validate GValue, and only
incidentally provides us with the facilities to implement properties on
GObject. GObject itself requires us to provide accessors functions and
then call them from within a huge switch() inside two virtual functions.
Property definitions should be able to either directly access a struct
field or specify the accessors pair that control a property. On top of
that, most of the property and accessor definition can be autogenerated
from simple pre-processor directives.
So, here's to you GProperty.
GProperty is a GParamSpec sub-class that encapsulates all the C
fundamental types inside a single, opaque structure (to avoid leaking
out implementation details); a GProperty can access the structure member
holding the value of the property, or invoke the accessor functions
passed to its constructor. Type safety is enforced at compile time
through the C type system, and at run time through the GType system.
GProperty will try *very* hard to avoid boxing and unboxing fundamental
type values into GValues.
GObject will recognize whether a GParamSpec used to set or get a
property is really a GProperty, and thus will shortcircuit most of the
GValue-based marshalled code, preferring the direct C function and
direct argument collection instead of boxing/unboxing of GValues.
https://bugzilla.gnome.org/show_bug.cgi?id=648526
For static types, it should be possible to register a private data
structure right when we are registering the type, i.e. from the
get_type() implementation. By allowing this, we can take advantage of
the existing type definition macros to cut down the amount of code
necessary (as well as the knowledge baggage) when creating a new type.
The main issue with this new feature is that it cannot be mixed with the
old idiomatic way of adding private instance data by calling a function
in the middle of the class_init() implementation, as that imposes the
additional constraint of initializing the whole type hierarchy in order
to retrieve the offset of the private data in the GTypeInstance
allocation.
For this reason we are going to follow a two-step process; in the first
step, we are going to introduce the new (semi-private) API to register
the intent to add private instance data from within the get_type()
implementation, and hide it behind a macro; at the same time, the
G_DEFINE_TYPE_EXTENDED macro is going to be modified so that it will
register the private instance data if the macro was used, using a new
(semi-private) function as well. Once we have migrated all our code, we
will make the first new function perform the actual private data
registration, and turn the second new function into a no-op. This should
guarantee a transparent migration of existing code to the new idiomatic
form.
https://bugzilla.gnome.org/show_bug.cgi?id=700035
Since we added g_object_notify_by_pspec(), an efficient way to install
and notify properties relies on storing the GParamSpec pointers inside
a static arrays, like we do for signal identifiers.
Instead of multiple calls to g_object_class_install_property(), we
should have a single function to take the static array of GParamSpecs
and iterate it.
https://bugzilla.gnome.org/show_bug.cgi?id=626919
Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>
GBinding is a simple, opaque object that represents a binding between a
property on a GObject instance (source) and property on another GObject
instance (target).
https://bugzilla.gnome.org/show_bug.cgi?id=348080
